This invention relates to a fusing apparatus for fusing wires to a commutator of an electric motor. More particularly, this invention relates to a fusing apparatus in which a temperature sensor is provided for controlling the fusing operation.
Conventional armature commutators are formed of copper alloy bars which are anchored to a core material to form a commutator surface. The lead wires from the wound armature are passed around hooks or "tangs" of the commutator, or are inserted into slots in the commutator. The wires are then fused to the commutator by applying pressure and heat.
Until recently, the core material which supports and anchors the bars of the commutator included asbestos, which was resistant to the effects of heat. The materials now being used to form the core of conventional armature commutators do not include asbestos and are more sensitive to heat. The structural characteristics of these new materials may be altered at temperatures which are lower than those required to affect materials including asbestos.
During fusing, a large amount of heat may be dissipated to the core materials through the commutator bars. The heat transferred to the core materials must be controlled, to prevent irreversible damage to the commutator. If the heat transfer is not controlled, the ability of the core materials to anchor the commutator bars could be impaired. This might result in, for example, the commutator bars coming loose when subjected to centrifugal forces developed during operation of the motor.
Thus it is important to monitor the heat flow from the fusing electrode to the core material of the commutator. It also is important to control the heat flow to maintain the temperature of the core material within a safe range of temperatures.